Compressor mechanism for internal combustion engines and the like



Feb. 19, 1963 Filed Nov. 24, 1958 A. N. ADDIE ETAL 3,077,731 COMPRESSOR MECHANISM FOR INTERNAL COMBUSTION ENGINES AND THE LIKE 6 Sheets-Sheet l Feb. 19, 1963 A. N. ADDIE ETAL 3,077,731

COMPRESSOR MECHANISM FOR INTERNAL COMBUSTION ENGINES AND THE LIKE 6 Sheets-Sheet 2 Filed Nov. 24, 1958 INVENTORS ATTORNEY Feb. 19, 1963 A. N. ADDlE ETAL 3,077,731

COMPRESSOR MECHANISM FOR INTERNAL COMBUSTION ENGINES AND THE LIKE Filed Nov. 24. 1958 6 Sheets-Sheet 3 INVENTORS Feb. 19, 1963 A. N ADDIE ETAL COMPRESSOR MECHANISM FOR INTERNAL COMBUSTION ENGINES AND THE LIKE Filed Nov. 24. 1958 6 Sheets-Sheet 4 INVENTORS ATTOENEY Feb. 19, 1963- A. N. ADDIE ETAL 3,077,731

COMPRESSOR MECHANISM FOR INTERNAL COMBUSTION ENGINES AND THE LIKE Filed Nov. 24. 1958 6 Sheets-Sheet 5 INVENTORS A TTOENEY Feb. 19, 1963 A. N. ADDIE ETAL 3,077,731

COMPRESSOR MECHANISM FOR INTERNAL COMBUSTION ENGINES AND THE LIKE Filed Nov. 24. 1958 s Sheets-Sheet e IN VEN T ORS United States Patent Office 3,077,731 Patented Feb. 19, 1953 3,977,731 CQMZPRESSUR MECHANISM FUR INTERNAL GUM- BUSTlfiN ENGINEE AND THE LIKE Albert N. Addie, La Grange Earth, and Brian M. Gallagher, Downers Grove, 1311., assignors to General Motors Corporation, Detroit, Mich, a corporation of Delaware Filed Nov. 24, 1958, Ser. No. 776, .w9 32 Claims. (@l. dd-dZ) This invention relates generally to a compressor mechanism; more particularly, to a combined or unitary compressor mechanism including a centrifugal compressor, an intake silencing means and/ or a rotary after-cooling heat exchanger; and with regard to certain more specific features of the invention, to such a combined compressor mechanism in combination with and adapted to supply pressurized charging air to an internal combustion engine power plant.

In operation, high speed centrifugal compressors generate a characteristic noise which normally consists of sound wave components distributed throughout the audible sound range spectrum. However, the higher frequency sound waves, i.e., 5,000 to 20,000 c.p.s., thus generated tend to dominate this noise and result in the auditory preception of a relatively high pitch whine. Such a high pitch whine is, at least, a source of extreme psychological annoyance and, as both the frequency distribution or quality and the magnitude or intensity level of the generated noise are generally functions of the speed and capacity of the compressor unit, these factors may be combined in certain installations to achieve a noise level in which is psychologically unbearable, going not only beyond a deafening level but even beyond the so-called threshold of feeling. Sustained exposure to such sounds produces a rapid deterioration of a persons hearing ability to a condition of permanent deafness.

Since the pressure discharge of a high speed compressor is generally connected to a sound attenuating pressure system, the noise generated by such a compressor emanates primarily from the compressor inlet. The invention thus contemplates a compact intake silencer arrangement which is capable of damping the sound waves emanating from the compressor inlet and particularly those higher frequency waves falling Within the above specified range.

In most compressor installations, a cooler or heat exchanger is generally required to cool the pressurized air discharge from the compressor thereby decreasing the volume and increasing the density of the compressed air. The invention further contemplates the provision of an improved structural arrangement of a centrifugal compressor and an air-to-air heat exchanger wherein the heat exchanger is built into and forms a cooperative part of the compressor unit. The invention still further contemplates the provision of an improved structural arrangement of a centrifugal compressor, an intake silencer and a cooler wherein each component is built into and cooperates to form a part of a unitary compressor mechanism.

As above defined, the combined compressor unit of the invention has particular application to the pressure charging of an internal combustion engine and, with regard to certain more specific features thereof, to the pressure charging of an internal combustion engine mounted in a vehicle, such as a locomotive, having a limited engine compartment. Ience, for the purpose of illustrating the invention, a preferred embodiment thereof is herein illustrated and described as applied to a turbocharging system for a locomotive engine of the two-cycle combustion ignition type. However, the invention is not considered to be so limited.

In its illustrative embodiment, the invention features the combination of a centrifugal compressor which is adapted to supply scavenging and charging air to a two-cycle engine and which is selectively drivable by the engine and an exhaust gas turbine or by the exhaust gas turbine alone; a silencer defining an intake duct connected to the inlet of the compressor and lined with sound absorbing material and including a rotatably driven axial flow fan member and stationary flow deflecting struts cooperating to impart limited swirl and pressure to the air flowing to the compressor inlet through the duct and to reflectively dampen the substantially unidirectional, high frequency sound waves emanating from the compressor inlet; and an air-to-air aftercooler including a matrix rotatably driven through the discharge passage of the compressor and a matrix cooling air passage defined in part by the intake silencer and intersected by an axial flow fan common to the intake silencer fan member.

In this illustrative embodiment, the engine compartment is connectable to the atmosphere outside the car body through a plurality of suitable filters and serves as an acoustical capacitance further tending to attenuate the noises emanating from the compressor inlet, particularly the lower, more audibly acceptable frequencies which otherwise might not be effectively silenced by the use of the high frequency intake silencer alone. By connecting both the compressor inlet and the cooling air inlet of the aftercooler to the interior of the engine compartment and discharging the matrix heated cooling air to the atmosphere outside the car body, the combined unit of the invention also serves to ventilate the engine compartment of the car body thus permitting the engine to operate under more ideal ambient temperature conditions.

The foregoing and other objects, advantages and features of the invention will become apparent from the following description of the preferred embodiment thereof, having reference to the drawings, wherein:

FIGURE 1 is a side elevational view of a locomotive car body with the engine compartment defining portion thereof enlarged and broken away to show the preferred illustrative embodiment of the invention and its operational environment in somewhat diagrammatic form;

FIGURE 2 is a view showing the unitary compressor, silencer and cooler of the preferred embodiment of the invention in detailed section and showing digrammatically the alternate turbine and engine drives of the compressor and the proportionate and reduced speed drives of the ducted fan impeller which is common to the intake silencer and the aftercooler;

FIGURE 3 is a transverse sectional view of the combined compressor, silencer and cooler unit taken substantially on the line 33 of FIGURE 2;

FIGURE 4 is an enlarged sectional view similar to and showing portions of FIGURE 2 in greater detail;

FiGURE 5 is an enlarged sectional view similar to and showing portions of FIGURE 3 in greater detail;

FIGURE 6 is another enlarged sectional view similar to and showing other portions of FIGURE 2 in greater detail;

FIGURE 7 is a development view taken substantially on the line 7-7 of FIGURE 6 and shows the angular relationship between the blades of the intake silencer and cooler air fans and their cooperating fiow deflecting vanes; and

FIGURE 8 is a sectional view similar to a portion of FIGURE 6 showing a modified form of the invention.

Referring more particularly to FIGURE 1 of the drawings, a locomotive car body is indicated generally at 10 and defines an engine compartment 12 in which a twocyole combustion ignition engine 14 is suitably mounted. The engine 14 is drivingly connected to a generator 16 which is operable to supply motive power to the several axle driving traction motors, not shown. The interior of the engine compartment is connected to the atmosphere ontside the locomotive car body through a plurality of car body filters, a few of which are shown at 18. Pressurized scavenging and charging air is supplied to the air box of the engine 14 by a turbocomprcssor indicated at 20.

In accordance with certain aspects of the invention, the turbocompressor mechanism 20 includes a centrifugal compressor 22 which is adapted to be both turbine and engine driven, an intake silencer 24, and a rotary air-toair heat exchanger 26, all cooperating to define a compact unitary structure which may be mounted on the accessory drive or timing gear housing 28 ot the engine and extends longitudinally therefrom in the compartment space immediately above the generator.

As best seen in FIGURE 2, the centrifugal compressor 22 includes a casing 30 rotatably mounting an impeller 32 and cooperating therewith to define a central intake chamber 34, and an annular dischargechamber 36. The inlet and discharge chambers 34 and 36, respectively, are interconnected by a plurality of flow-inducing, radiallyextending passages which are defined between the impeller vanes. The compressor discharge chamber 36. is embraced by a ring 38 of circumferentially spaced, curved diffuser vanes which define a plurality of passages through which the velocity of the airdischarged from the periphcry of the impeller is converted into fluid pressure in a well understood manner. Thepressurized air flowing radially outwardly from the diffuser. 38 passes into an annular discharge chamber or scroll 4%. An arcuately extending opening 42formed in the periphery of the scroll 40 is connectable to the air box of the engine through the rotary air-to-air heat exchanger 26 and two impingement typeair filters indicated at 44.

Thecompressor impeller 32 is mounted on one end of a hollow shaft 46 which may be integral with the hub of an axial flow turbine wheel 48, projecting therefrom in opposite directions, as shown. The exhaust gases of the engine 14 flow through an exhaust manifold 50 extending longitudinally of the engine to a turbine inlet scroll 52which is connected thereto at its turbine-adjacent end. The exhaust gases supplied to the inlet scroll 52 are directed through a nozzle ring 54 against the blades 56 of the turbine wheel thereby driving the turbine. The exhaust gases discharge from the turbine wheel through an annular exhaust diffuser 58 into an annular discharge chamber or scroll 60. The discharge scroll 60 is in turn connected to the atmosphere outside the locomotive car body by a suitable exhaust stack 62. The turbine 4-8 is thus operable to drive the compressor in accordance with thesupply of engine exhaust gases thereto.

To provide sufiicient pressurized air for scavenging and charging the. two-cycle engine 14 during periods of low speed engine operation and engine acceleration, the turbocompressor unit 22 is preferably provided with a mechanical drive 66 intermediate the engine and the compressor which includes an overrunning drive control means operable to drivingly connect the compressor to the engine Whenever the mechanical engine drive is being driven taster than the turbine and operable to disconnect the compressor. from the engine whenever the turbine is being rotatably driven by the exhaust gases at a rate faster than would be provided by the mechanical drive.

The mechanical drive 66 includes an external gear 64 which is formed adjacent the end of the hollow shaft 46 opposite the compressor. The gear 64 serves as the sun gear of a planetary gear set. The sun gear 64 meshes with a plurality of equi-angularly spaced planetary gears 68. which are rotatably supported at 72 by a planetary carrier 70. A stub shaft 76 integral with the planetary carrier70 is suitably journaled, as indicated at 74, in the turbocompressor casing. A driving gear 78 secured to the carrier shaft '7 6 meshes with and is driven by an engine driven accesory drive gear 80. The planetary gears 68 mesh with a ring gear 82 which. is rotatably mounted in the turbocornpressor casing, and connectable thereto by an overrunning drive control mechanism 86 to provide engine drive of the compressor impeller when the engine drive is rotating faster than the drive which would otherwise be provided by the turbine.

The drive control mechanism 86 is shown in FIGURE 2 by a conventional symbol representing an overrunning clutch or brake device wherein rotation of the carrier and its shaft in the direction of the arrow A providing a compressor speed taster than that possible with the available exhaust gases supplied to the turbine tends to rotate the ring gear 82 in the same rotational direction and effects the braking of the ring gear to the stationary casing or frame member 84. When the compressor drive effected by the exhaust gas driven turbine is faster than that which would be provided by the mechanical drive from the engine, the relative rotation between the carrier and the turbine-compressor shaft 46 eiiects the opposite direction of rotation of the ring gear 82 thus causing drive control mechanism as to overrun or free wheel relative to the stationary frame or casing member 84 thereby effectively disconnecting the turbocompressor from its engine drive.

The compressor discharge scroll serves to support the combined intake silencer and aftercooler assembly 24, 26 relative to the compressor casing 30. In the illustrative embodiment the scroll-defined discharge chamber 49 is [formed between the outer diffuser portion of the compressor casing 3%, an inner cylindrical member 46', and an outer annular member 46''. The member 4d also serves to partially form the arcuate discharge opening 42. The cylindrical member 44V extends longitudinally from the diffuser portion of the compressor casing and is spaced concentrically of the compressor inlet. The member ltl" embraces the member 40' and is secured thereto adjacent its end opposite the diffuser and, except for its discharge opening defining portion, extends longitudinally therefrom to the compressor casing radially outwardly of the diiiuser outlet to partially define the discharge chamber 46. As best seen in FIGURE 3, this chamber-defining portion of the member 40" extends through an angle or approximately 240 and terminates adjacent its discharge opening defining portion. This last-mentioned portion of the member 40 is flared longitudinally away from its chamber-defining portion.

A frusto-conical spider member 90 extends longitudinally and radially outwardly from the end of the cylindrical scroll member 4t), being nested with and secured outwardly to the last-mentioned portion of the member 4t)"; The spider E 0 serves as an intermediate support member for the aftercooler 26 and has a plurality of arcuately extending ports 96 extending therethrough. The ports it subtcnd the major portion OLE the spider and are defined by struts of limited angular width which extend between the flanged ends of the spider.

The aftercooler 26 includes an outer casing 92 which cooperates with the structure of the intake silencer 24 to define a cooling air duct 94; a cylindrical air-to-air heat exchanging matrix 96 which is rotatably mounted and sealed with respect to the casing 92 to require heat exchanging air flow therethrough; and an axial flow fan 98which is operable to induce the flow of cooling air through the matrix and the cooling air duct 9'4.

The aftercooler casing 92 includes an annular end plate which extends radially outwardly from the periphery of the compressor casing. A second annular plate 102 extends radially outwardly of the spider 90 in parallel relation to the plate 100. The outer peripheries of these plates are of identical configuration. As best seen in FIGURE 3, the upper portion of each of these plates is partially defined by an arcuate surface which is formed on a radius R about the axis of the compressor and subtends an angle slightly less than that subtended by the discharge chamber forming portion of the scroll member 40'. Two flat surfaces extend tangentially from the opposite ends of this arcuate surface and intersect a second arcuate surface which is formed on a radius R about the axis of the generator 16. This configuration of the lower portion of each plate permits the compact, relatively close radially spaced mounting of these plates, and thus of the aftercooler, immediately above the generator housing while providing relatively large openings for the flow of the cooled pressurized air from the aftercooler to the inlet passages of the flanking impingement filters 44. In this connection, it will be noted that these tangential surfaces are radial to the generator axis, and define planes which are symmetrical with respect to a vertical plane common to the axes of both the turbocharger and generator.

As shown in FIGURE 3, two angled members 1M and 1% constitute frame members extending intermediate the lower portions of the casing plates The and M2. Each of these members has a major leg portion M and 1%, respectively, which is outwardly coextensive with the corresponding, longitudinally aligned tangential surfaces of the plates 1% and M2. The legs led and tilt define outlet ports 1% and 167, respectively, which are suitably connectable to the flanged inlet ducts of the symmetrically arranged impingement filters, as indicated at Tilt and 116, respectively. The bottom of the casing 92 intermediate the plates 1% and 1102 and the portdefining legs of the members 1% and 1% is closed by a plate lld l which extends longitudinally between and conforms to the lower arcuately defined peripheral surfaces of the plates Hill and 162. The upper portion of the aftercooler casing between the plates Tilt and it is embraced by a perforated cooling air intake screen 103 which extends arcuately between the upper ends of the members lib-l and res and longitudinally between the plates lltlil and 1&2 and is suitably secured to the several casing members.

The minor legs 104- and 1656" of the members litl and res, respectively, extend radially inwardly toward the common rotative axis of the several elements of the combined turbocharger unit from the upper end of the major legs 104' and res. As best seen in FIGURES 3 and 5, the longitudinally disposed ends of these radially extending minor legs NM and ice" are each provided immediately adjacent the casing plates 1% and T02 with bosses or lugs M2 and 114, respectively, which extend laterally and downwardly therefrom. paired bosses 112 and ltd support the opposite ends of shafts T16 and 118, respectively, upon which cylindrical guide rollers 12d and 122, respectively, are suitably journaled. The guide rollers 12% and 122 in turn rotatably support or cradle the cylindrical heat exchanging matrix The matrix drum 96 is also rotatably supported internally by longitudinally extending guide rollers 124 and 126 which engage its inner surface opposite the rollers llil and T22, respectively. The inner guide rollers T24 and 126 are suitably journaled on shafts and 13%, respectively, which are supported at their opposite ends by paired bosses or lugs 132 and 1354, respectively. These bosses extend laterally and downwardly in parallel spaced relation to the bosses 112 and 114, respectively, from partition members 136 and 138 which extend longitudinally between the casing plates Tilt and N2 in radial alignment with the legs ill s" and res", respectively.

As rotatably mounted by the guide rollers 12%), 122, 124 and 126, the matrix drum 96 spacedly embraces the compressor discharge scroll 4b and the spider 9d and ro tatably passes the arcuate discharge opening 42. The matrix drum comprises two annular end plates Mill and a plurality of radial plates or strips 142 (see FIGURE 3) which extend longitudinally therebetween. The spaces intermediate the end plates l t-(l and the strips 142 are packed with a suitable porous heat exchanging material indicated at 144, such as a woven or spun metal gauze, and define a plurality of substantially radial heat exchanging air flow passages therethrough. The end plates Mil These of the drum for each provided with external gear teeth indicated at 146. These gear teeth drivingly engage the mating gear teeth of two pinion gears 148 which are secured to an engine-driven shaft 15% in longitudinally spaced relation to each other. A suitable driving conection between the pinion drive shaft 15% and the engine-driven accessory drive gear 82' is indicated diagrammatically in FXGURE 2 by the line 152 extending between these gears.

The longitudinal ends of the matrix drum are sealed with respect to the casing plates Tilt) and 162 by seals 154 extending therebetween. As best seen in FIGURE 4, each of the seals 15 includes a seal ring 155 of a suitable material, such as Teflon, which is heat resistant and capable of being biased into nonlubricated rotative sealing contact with the adjacent radially extending face of one of the matrix end plates 14%. The relatively flexible seal ring 155 is preferably backed by a relatively more rigid metal ring T56 and an annular flexible diaphragm seal member 157 is interposed between the backing ring and the adjacent casing plate. The diaphragm seal 157 is preferably made of a highly heat resistant flexible material, such as silicon rubber, and may be fabric reinforced. The seal ring 1155, the backing ring 156 and the adjacent end of the flexible diaphragm member 1557 may be secured together in any suitable man ner, such as by a plurality of equiangularly spaced rivets as indicated at 158. The opposite end of the flexible diaphragm member is somewhat similarly secured to the adjacent casing plate by suitable but detachable means, such as a plurality of equiangularly spaced nuts and bolts as indicated at The longitudinal movement of the seal and backing rings it'd and 155 relative to the casing plates 1% and Th2 and the matrix end plates Mt is guided by a plurality of equiangularly spaced pins res. The pins see are carried by and project axially from the backing ring and are telescopically and guidingly embraced by the adjacent ends of hollow cylindrical pins 162 which are carried by the casing plate. Each of the hollow pins 152 is closed at its opposite end and a relatively light spring 163 is compressively interposed in its hollow portion between its closed end and the backing-ring-carried pin 16% projecting therein. The springs 153 thus serve to bias the backing ring and the seal ring carried thereby into relatively light rotative sealing engagement with the axial face of the adjacent matrix end plate Mil.

In addition to its guide roller supporting function, each of the minor legs 1%" and Hi5 of the members 1-34 and 1% forms a radially extending partition wall and carries a radially adjustable close clearance seal 166 and 168, respectively, which seals its supporting partition wall with respect to the external surface of the matrix. The guide roller supporting partition members 136 and 133 similarly carry radially adjustable close clearance seals 17%) and 172, respectively, which seal their respective partition members with respect to the inner surface of the matrix. it will thus be seen that the several partition defining members and the several seals divide the casing intermediate the plates 1% and 162 into an airheating or matrix-cooling chamber 174 and an air-cooling or matrix-heating chamber T76.

The close clearance seals 16%, 179 and 172 are substantially identical with the close clearance seal 166 which is shown in enlarged detail in FIGURE 5. Each of these close clearance seals comprises a channel-shaped member llliti which is carried by and extends longitudinally of the partition portion of the member lild between the roller supporting lugs 112. The channel defining side walls of the member 18% slidably mount a longitudinally extending T-shaped seal pad 182 which is radially adjustable by four screws 18 two adjacent each end thereof, to vary the radial clearance between the matrix and its clearanceder'ining surface. Each of the screws 1554 is provided with a reduced diameter portion 184' threadanswer ableinto the cam pad member with one hand of rotation and a larger threaded portion 184" which is threadable through the channel-shaped member with the opposite hand of rotation. Due to the use of threads of opposite hands adjacent the opposite ends of the screws 184, rotation of these screws in opposite directions effects alternate variations in the radial clearances intermediate the matrix and the cam pad. For the purpose of eifecting such clearance adjustments, the larger channelengaging ends of the screws 184 are each provided with sockets, as shown at 186, which are adapted to receive hexagonal wrench members of the Allen type.

The outer duct defining casing 92 of the aftercooler 26 further comprises a cylindrical member 1% which is supported by and extends longitudinally from the flanged outer end of the spider member 99. The member 1% converges frusto-conically inwardly to the cylindrical throat portion 190 of constant diameter. This constant diameter throat portion embraces the axial flow fan S t; and cooperates with the portions of the intake silencer 24 which it spacedly embraces to define an annular duct of constant dimension through the fan 98. The throat end of the member 196 mates coaxially with a second cylindrical duct member 192 and is connected thereto by a resilient coupling indicated at 194. The duct member 192 is secured at its opposite end by suitable means to a. discharge header 1%. The header 1% defines an upwardly extending duct or opening 198 which is connected by a resilient coupling 202 to an exhaust stack 200. The exhaust stack 2% is mounted in the car body and extends to the atmosphere outside the engine compartment. The end of the header member 1% opposite its connection to the member 192 is provided with an opening 264 which embraces and supports an air inlet assembly 2 06.

The inlet assembly 206 forms a part of the intake silencer 24- and supports the adjacent end of an intake duct defining section 226 of the silencer. This inlet assembly comprises a cylindrical member 2% which is embraced by and supported in the header opening 204. The member 203 in turn telescopically embraces and supports the adjacent end of the silencer section 226. An annular air intake screen 210 is sandwiched between the flanged end of the member 208 and a mating flange formed on the adjacent end of an annular intake bell 212 and extends radially inwardly therefrom.

A plurality of deflector blades 216 and 218 extend radially of the throat portion of the fan duct and respectively serve to introduce the air deflectively into and to receive the air discharged from the blades 22% of the cooling air fan 98 in a well known manner. The blades 220 of the fan member 98 are rooted in an annular rim 221 which extends intermediate the cooling air duct 94 and the silencer defined intake duct. The discharge deflecting blades 218 are carried by and extend radially inwardly from the duct defining member 190 to an inner ring 222. The ring 222 carries a seal ring 22d which cooperates with the fan rim 221 to provide a labyrinth seal 225 therebetween. The ring 222 also telescopically supports the adjacent end of the intake silencer duct section 226 which extends longitudinally therefrom to its inlet end which, as mentioned above, is supported by the cylindrical member 294 of the air inlet assembly.

A second intake duct defining section 2280f the silencer 24 is supported by the coaligned adjacent flanges of the scroll member 40 and of the frusto-conical spider 9t} and extends longitudinally therefrom to a point immediately adjacent the fan rim 221. The fan adjacent end of the section 228 carries a ring 230 which in turn mounts the several fan inlet deflector blades or vanes 216. The deflector ring 230 also mounts a seal ring 232 which cooperates with the fan rim 221 to provide a multiple labyrinth seal 234 therebetween.

Due to the complex nature and high level of noise which is generated by the compressor and would otherwise emanate from the compressor inlet, the intake silencer 24 is preferably a multistage silencing device particularly adapted for dampening or silencing of the extremely unpleasant higher frequency sound waves charcteristic of such high speed centrifugal compressors.

In addition to the duct defining sections 226 and 228, the intake silencer 24 includes several other duct defining sections 236, 238 and 240. These sections are coaxially aligned with the compressor and its inlet and cooperate to define an intake duct 242 of annular cross-section converging toward and connecting the inlet chamber of the compressor to the interior of the vehicle compartment 12. The fan member 98 intersects the intake duct 242 and divides it into a first portion 242' defined between the sections 226 and 236 and a second portion 242" defined between the sections 228, 238 and 240.

The fan member is perforated to define a plurality of axial flow inducing fan blades 252. These blades extend radially between the fan rim 221 and the impeller hub 254- and, as best seen in the development of FIGURE 7, are inclined to induce air flow axially in the intake duct toward the compressor inlet. The cooling air fan blades 229 are of course oppositely inclined to effect air flow in the opposite direction in the cooling air duct 94. The fan impeller @d is supported and driven by a shaft 256 which is journaled immediately adjacent its fan end in a bearing 25$. As shown in FIGURE 6, the bearing 258 is supported by the silencer section 228 through a plurality of stationary deflector vanes 260 which depend radially inwardly from its fan adjacent end and terminate in a bearing supporting rim or hub 262. The vanes 260 cooperate with the fan blades to impart a limited helical swirl to the air flowing to the compressor inlet. This swirl is preferably complementary to the configuration of the vane-defined radial passages of the compressor impeller and provides a reduced inducer angle of attack for the air entering the compressor at all fan and compressor speeds thereby increasing the range and capacity of the compressor.

The opposite end of the shaft 256 is splined, as indicated at 264, to the end of a quill shaft 266. The quill shaft 2&6 extends through the hollow turbine drive shaft 45 and its distal end is drivingly splined, as indicated at 268, to the stub shaft 76 of the engine driven planetary carrier 7%. The shaft 265 is journaled by a bearing 270 immediately adjacent its splined connection to the shaft 256. The bearing 279 is mounted in an inlet hub portion 3% of the compressor casing, This hub portion is in turn supported and centered in the compressor inlet chamber 34 by a plurality of equiangularly spaced radial struts 39" which extend between the hub and the outer inlet defining portion of the compressor casing. A cap 272 secured to the end of the inlet hub 30 retains the bearing 276 in its mounted position and carries a rotary shaft seal 274 which sealingly embraces the splined end of the shaft 256. The bearing assembly 276 is sealed with respect to the compressor inlet by a rotary shaft seal 276 interposed between the inlet hub and the shaft 266 and by a pressurized air seal 278. Pressurized air for the air seal 273 is delivered thereto from the compressor outlet chamber 36 by a bleed passage 286} which is formed in the compressor casing and extends to the air seal through one of the radial struts 39".

The several duct defining sections of the silencer 24 also define a plurality of sound attenuating chambers which are connected to the intake duct. The sections 226, 228, 236 and 233 are each in the form of canisters of toroidal configuration and define sound attenuating chambers which are preferably packed with a suitable porous, sound absorbing material, such as steel wool or spun glass, as indicated at 226', 228', 236' and 233, respectively. The duct defining walls of these sections are suitably perforated as indicated at 226", 228", 236" and 238".

The sections 226 and 236 are both of constant radial dimensions and are concentrically spaced with the inner section 236 being supported relative to the outer section 226 by a plurality of straps 244- and 246 which extend radially therebetween adjacent their ends. The inlet portion 242 of the silencer defined intake duct 242 is thus of constant annular cross-section. The end of the section 236 adjacent the air inlet assembly 2% is provided with a hemispherical closure cap 248. This cap is telescopically embraced by the air inlet screen 216 and cooperates with the air inlet bell 212, which is radially spaced therefrom, to define an annular air inlet 250 of converging configuration. The opposite end of the section can is mounted in limited spaced relation to the im-i peiler hub 254 and cooperates therewith to define a central sound attenuating chamber 282 connected to the intake duct M2 immediately adjacent the roots of the blades 252 through the limited annular clearance 234 therebetween.

The silencer sections 228, 238 and 240 which define the intake duct portion 242" intermediate the fan and the compressor inlet are of frusto-conical longitudinal configuration and cooperate to provide convergence of this portion of the intake duct from the fan to the compressor inlet. The section 244) extends between the section 223 and the compressor inlet and provides a duct defining surface coextensive with that of the section 228. The inner duct defining section 238 is supported at its fan adjacent end by the bearing supporting rim 262 and at its compressor end by the bearing retaining cap 272. The chamber 23S defined within the section 238 and thus the sound absorbent packing therein is of constant radial dimension throughout its length although the area thereof presented to the intake passage progressively increases away from the compressor inlet. The chamber 228 is of trapezoidal frusto-conical longitudinal cross-section with divergence of its radial dimension toward the compressor inlet thus progressively increasing the depth of the sound absorbent material packed therein as presented to the intake duct. A conical chamber 286 is formed centrally of the section 238. This chamber may be connected to the intake duct by a series of perforations 288 immediately adjacent its fan adjacent end to form another sound attenuating chamber. A similar sound attenuating chamber may be provided by connecting the intake duct through a plurality of perforations indicated at 292 to a chamber 290 defined between the cylindrical scroll member an, the compressor housing, the duct defining section 24%) and the adjacent end of the section 228.

In a typical application of the above-described unitary turbo-compressor, heat exchanger, and air intake silencer, the accessory drive or timing gear train of the engine 14 is such that the planetary carrier shaft "76 is driven at approximately 2,800 rpm. at a maximum engine speed of 900 rpm. The drive ratio of the auxiliary gear drive 152 is such that the matrix 36 is driven at a speed of ap proximately 70 rpm. at the maximum rated engine speed. in the absence of exhaust gases suflicient to overdrive the turbine relative to the mechanical drive, as during engine starting or accelerating periods, the accessory drive gear train of the engine will partially drive the compressor impeller 32 through the planetary gear set providing a maximum engine driven compressor speed of approximately 16,230 rpm. at the maximum rated engine speed. However, as the engine load and speed increases, the exhaust gases from the engine will progressively increase until the turbine overdrives the mechanical drive 66. As.

the engine approaches full load and speed operation, the exhaust gases will normally be suflicient to drive the turboco-mpressor at a speed of 19,000 to 20,000 rpm.

In operation, air is drawn into the engine compartment 12 through the several car body filters 18 by the combined suctions of the compressor 22 and the axial flow fan 93..

As indicated above, the intake fan blades 252 serve as a limited first stage of compression inducing air flow in the intake duct toward the compressor inlet. However,

the pressure rise effected by these intake fan blades is preferably restricted to less than one inch of Water at the compressor inlet thus minimizing the driving power absorbed thereby. In addition to providing this limited first stage of compression, the fan blades 2E2 serve as a driving connection intermediate the fan hub 254 and the outer fan rim and blades 221 and 220, respectively. In cooperation with the air flow deflecting vanes sea, the fan blades 252 also impart a helical swirl into the air flowing to the compressor inlet. This fan induced swirl varies with driving speed of the shaft 256 and tends to be complementary to the radial passages defined by the impeller vanes 32 providing means for substantially reducing inducer angle of attack at all engine and compressor speeds. Such reduction of angle of attack increases the flow range or capacity of the compressor. As explained in somewhat greater detail below, the fan blades 252 also cooperate with the stationary vanes ass to reflectively and deflectively dampen the substantially unidirectional high frequency sound waves emanating from the compressor inlet.

The air discharged from the compressor passes through the diffuser 38 into the compressor discharge scroll 40. It then passes through the rotating matrix 96 in the air cooling chamber 175, transferring a portion of the compression induced heat from the pressurized air to the matrix. After passing through the matrix, the relatively cool pressurized air is delivered through the impingement filters to the engine air box. As the heated matrix rotates through the matrix cooling chamber 174, the heat imparted to the matrix by the pressurized air is transferred to the cooling air flow induced by the axial flow fan 93 thus cooling the matrix 96. The cooling air heated by the matrix passes through the fan $8 and is then discharged outside the car body through the exhaust stack 2%.

As indicated above, the high frequency sound Waves generated by the compressor impeller are substantially unidirectional and highly echoic. In passing outwardly of the annular intake duct, a portion of such waves initially strikes the duct defining surfaces of the silencer section 238, being partially absorbed by the packing material 238' and partially deflected thereby toward the sound absorbing sections 226 and 228. A second portion of the high frequency sound waves emanating from the compressor inlet are directed toward the duct defining surfaces of the silencer sections 226 and 228, being similarly partially absorbed by the packing material of such sections and partially deflecting therefrom. A third portion of the compressor generated high frequency unidirectional waves are directed longitudinally of the intake duct and, in the absence of the sound reflection and deflection cooperation of the fan and stationary vanes 252 and 269, respectively, would normally pass outwardly of the silencer unit without possible deflection and absorption by the duct defining surfaces and chambers of the several silencer sections. The fan blades 252 are of a configuration and equi-angularly spaced so that substantially all of the higher frequency sound waves reaching the intake fan area, either directly from the comressor inlet or by deflection, are deflected by the fan blades. The sound waves deflected by the fan blades are directed toward the adjacent sound absorbing surfaces and chambers of the several silencer sections. A portion of the sound waves deflected by the fan are further deflected by the stationary vanes 26!) to be effectively reflected back to the compressor inlet in out-ofphase relation thereby effectively dampening the sound waves emanating therefrom.

From the foregoing description of the operation of the intake silencer, it will be seen that this intake silencer 24 is primarily anechoic being designed to reflectively and deflectively dampen the higher frequency sound waves emanating from the compressor inlet. However, a substantial portion of the lower frequency sound waves generated by the compressor as well as a limited portion of the higher frequency sounds are also attenuated by the acoustical capacitance provided by the chambers 282, 286 and 2%. Any sound Waves passing outwardly of the silencer intake duct 242, and particularly the lower frequency waves, are further attenuated by the acoustical capacitance provided by the engine compartment 12.

,In certain installations requiring a higher degree of noise abatement or where space limitations require the intake duct defining silencer sections to be of less than optimum sound absorbing length or capacity, further anechoic silencing of the compressor generated high frequency sound waves may be desirable. As shown in FIGURE 8, an additional stage of anechoic silencing may be provided in such installations by a silencer assembly 3% including an anechoic target bafile 302 spaced axially of the intake duct nozzle bell 2-12 and an annular directionalizing bafile 3124 which spacedly embraces the outer periphery of the intake bell and the anechoic target- The target bafile 36-2 comprises a plurality of plates 308 which are mounted in spaced parallel relation transversely of a circular mounting plate 396 and extend longitudinally therefrom toward the intake bell. A cylindrical member 310 issecured to the periphery of the plate 3% and defines a. wall embracing the parallel plates 3% which areof varying lengths limited to the chordal dimensions imposed by the mounting plate 306 and the wall member 319. The plates 3% are tapered away from the mounting plate to provide a plurality of sound deflective surfaces or wedges which are covered with suitablevsound absorbing material 312 such as spun glass blanket type insulation. The exposed surfaces 314 of the spun glass blanket material lining the plates 308 are preferably spray coated with a thin vinyl film inter locking the exposed glass fibers to prevent erosion by the intake air flow. Wire cloth screening 316 may also be used to provide additional erosion protection of the exposed fiberglass material.

The annular directionalizing bafi le 304 cooperates with the cylindrical wall member 310 to define an annular air intake 313 and requires a change of direction of any sound waves emanating past the target bafile member. The directionalizing bathe comprises a cylindrical casing 32th of angled cross-section having a radial flange 322 embracing the intake bell 212 with slight radial The casing 329 may be sup-.

clearance therebetween. ported by a suitable bracket 324 carried by the generator 16 and in turn supports the target bafile 302 by means of a plurality of radial straps 326. The casing 320 is lined with sound absorbing insulation material 328, simi lar to that lining the anechoic wedges of the target bafile, which may be similarly spray coated with a thin vinyl film and covered with wire cloth screening 330 to prevent erosion by the intake air fiow.

The distance between the target baffle and the nozzle and the diametrical dimensions of the target and directionalizing baffie members are preferably such that a tangent, indicated in broken lines at 332, to the bell 212 and: passing through the peripheral face 334 of the directionalizing bafile intersects the cylindrical Wall member 310 of the target assembly 302. It will be seen that the bafile members of this additional stage of silenc-' ing thus cooperate to provide a combined dissipative and a non-dissipative reaction muffier achieving noise reduction partly by deflection and absorption of the sound energy emanating from the intake nozzle 212 and partly by reflecting the wave energy back toward the compressor source.

From the foregoing description of the several forms of the invention, it will be obvious to those skilled in the art that various changes might be made in the illustrative embodiments without departing from the spirit and scope of the invention as defined in the following claims.

We claim:

1. In combination, a housing member having an engine compartment therein, an internal combustion engine mounted in said compartment, filter means connecting the interior of said compartment to the atmosphere outside the compartment, means for supplying pressurized charging air to said engine including a casing, a compressor rotatably mounted within said casing, said compressor having an inlet connectable to the interior of said engine mounting compartment and a discharge connectable to said engine, said compartment and filter means defining acoustical impedance means operable to damp the sound waves generated by and emanating from said compressor and said engine constituting a high frequency sound attenuating means connected to said compressor discharge, turbine means operable to rotatively drive said compressor at a relatively high speed in no cordance with engine exhaust gases, supplied thereto, manifold means for supplying engine exhaust gases to saidturbine means. and therefrom to the atmosphere outside the compartment, mechanical drive means intermediate the engine and the compressor and including overrunning. means operable to drivingly connect said compressor to said engine under low exhaust gas supply conditions to said turbine, said; drive means being operable to disconnect said compressor from said engine whenever said turbine means is rotatably driven faster than said mechanical drive means, whereby said compressor is partially engine driven when said mechanical drive means is being driven faster than said turbine,

means and said turbine drive means is permitted to overrun said mechanical drive means whenever said turbine.

drive means is being driven faster than said mechanical drive means, high frequency silencer means associated with the inlet of said compressor and defining an annular intake duct converging toward and connecting the inlet of said compressor to the interior of said compartment, a first fan means intersecting said silencer duct and operable to impart limited pressure and swirl to the air flowing to the compressor inlet thereby increasing the efficiency and air flow characteristics of the compressor and to refiectively dampen substantially unidirectional high frequency sound Waves emanating from the inlet of said compressor, drive means intermediate said engine and said first fan means, an annular discharge manirold defined by said casing and embracing the discharge of said compressor and connected thereto by an annular diffuser, said annular discharge manifold having an arcuate outlet opening therein, a cylindrical heat exchange matrix embracing said annular manifold and supported by said casing for rotation past said manifold opening, seal means interposed between said matrix and said casing and cooperating therewith to define a matrix cooling chamber and a compressed air cooling chamber, passage means including sound attenuating impingement filter means connecting said air cooling chamber to said engine, means for drivingly connecting said matrix to said engine, said silencer means and said casing defining a cooling air duct therebetween embracing said intake duct, said cooling air duct connecting said matrix cooling chamber to the interior of said compartment and to the atmosphere outside said compartment, and a second fan means drivingly connected to said first fan means and operable to induce cooling air flow through said matrix from the interior of said compartment to the atmosphere, said cooling air duct and the relatively low velocity cooling air flow induced therethrough cooperating to insulate and attenuate sounds transmitted radially ouwardly of said intake duct.

2. In. combination, a housing member having an engine compartment therein, an internal combustion engine mounted in said compartment, filter means connecting the interior of said compartment to the atmosphere outside the compartment, means for supplying pressurized charging air to said engine including a casing, a high speed rotary compressor mounted in said casing, said compressor having an inlet conne-ctable to said engine mounting compartment and a discharge connectable to said engine, silencer means associated with the inlet of said compressor and defining an intake duct connecting the inlet of said compressor to said compartment, said silencer means including a first fan means operable to impart limited pressure and swirl to the air iiowin through said duct to the compressor inlet and to reflect substantially unidirectional high frequency sound waves emanating from the inlet of said compressor thereby damping such waves, said casing defining a discharge manifold interconnecting the discharge of said compressor with said engine, said manifold having an opening therein, a cylindrical heat exchange matrix supported for rotation by said casing and intersecting said manifold through said manifold opening, seal means interposed between said matrix and said casing and cooperating therewith to seal said matrix relative to said manifold and to define a matrix cooling chamber outside said manifold, said matrix cooling chamber interconnecting the interior of said compartment to the atmosphere outside the compartment, secondary fan means operable to induce cooling air flow through said matrix and said cooling chamber from the interior of said compartment to the atmosphere, and means operable to drive said compressor, said matrix, and said fan means at substantially proportionate and predetermined rotative speeds varying in accorda ce with the operation of the engine.

3. In combination, a housing member having an engine compartment therein, an internal combustion engine mounted in said compartment, filter means connecting the interior of said compartment to the atmosphe e outside the compartment, compressor means operable to supply pressurized charging air to said engine, said compressor means having an inlet connectable to the interior of said engine mounting compartment and a discharge connected to said engine, said compartment and filter means defining acoustical impedance means operable to insulate and damp sound waves generated by said compressor and engine, said engine constituting a high frequency sound attenuating means connected to the discharge of the compressor, turbine means operable to drive said compressor means in accordance with engine exhaust gases supplied thereto, mechanical drive means intermediate the engine and the compressor means and including overrunning means operable to drivingly connect said compressor means to said engine and operable to disconnect said compressor means from said engine whenever said turbine means is being rotatably driven faster than said mechanical drive means, whereby said compressor means is partially engine driven when said mechanical drive means is being driven faster than said turbine means and said turbine drive means is permitted to overrun said mechanical drive means whenever said turbine drive means is being driven faster than said mechanical drive means, silencer means associated with the inlet of said compressor means and defining an intake duct connecting the inlet of said compressor means to the interior of said compartment, a fan means associated with said intake duct and operable to impart limited pressure and swirl to the air flowing to the compressor inlet thereby increasing the efficiency and air flow pumping characteristics of the compressor and said fan means being capable of reflective dampening of the substantially unidirectional high frequency sound waves emanating from the inlet of said compressor, and drive means intermediate said engine and said fan means and operable to drive said fan means at a proportionate and substantially lower rotative speed than the sound-generating and air-flow-inducing driven rotative speed of said compressor.

4. In combination, an internal combustion engine, a high speed rotary compressor operable to supply pressurized charging air to said engine and having an inlet connectable to atmosphere and a discharge connected to said engine, silencer means associated wtih and defining an intake duct connected to the inlet of said compressor, fan means operable to impart limited pressure and swirl to the air flowing through said intake duct to the compressor inlet and said fan means being capable of reflective dampening of the substantially unidirectional high frequency sound waves emanating from the inlet of said compressor, and drive means intermediate said engine and said compressor and fan means and operable to drive both said compressor and fan means at rotative speeds proportional to the speed of the engine with the driven speed of said fan means being substantially slower than the sound-generating and air-flow-inducing driven speed of said compressor.

5. in combination with an internal combustion engine, means for supplying pressur zed charging air to said en gine including a high speed rotary compressor having an inlet connectable to the atmosphere and a discharge connectable to said engine, a discharge manifo'd interconnecting the discharge of said compressor with said engine and having an opening therein, a cylindrical heat exchange matrix supported for rotation and intersecting said manifold through said manifold opening, seal means interposed between said matrix and said manifold, duct means defining a matrix cooling chamber outside said manifold, fan means operable to induce cooling air flow through said matrix and said cooling chamber, and means operable to drive said compressor, said matrix, and said fan means at different rotative speeds proportionate to and varying in accordance with the operation of the en'- gine to provide substantially even charging air temperature under all engine operating conditions.

6. In combination, an internal combustion engine, means for pressure charging said engine including a compressor means capable of being rotatably driven, turbine means drivingly connected to and operable to drive said compressor means in accordance with the engine exhaust gases supplied thereto, overrunning drive means intermediate said engine and said compressor means and operable to drivingly connect said compressor to said engine when said engine drive means is rotating faster than said turbine driving means whereby said compressor means is both engine and turbine driven under such operating conditions and said overrunning drive means being operable when said turbine means is rotating faster than said engine drive means to permit said turbine to overrun said engine drive means, silencer means associated with the inlet of said compressor and defining an intake duct connecting the inlet of said compressor means to the atmosphere, a first fan means in said intake duct and operable to impart limited pressure and swirl to the air supplied to said compressor inlet, said first fan means being capabie of reflecting unidirectional high frequency sound waves thereby damping such waves emanating from the inlet of said compressor, a diffuser connecting the discharge of said compressor to a discharge manifold, said discharge manifold having an opening therein, a cylin drical heat exchange matrix supported for rotary movement relative to said manifold opening, seal means interposed between said matrix and said manifold, a second fan means associated with said matrix and operable to induce the flow of cooling air through the portion of said matrix outside said manifold, and means for drivingly connecting said matrix and said fan means to said engine, said last-mentioned means being operable to drive said matrix at a substantially lower rotative speed relative to its driving speed of said fan means.

7. In combinaation, a housing member defining an engine compartment, an internal combustion engine mounted in said compartment, filter means connecting said compartment to the atmosphere outside the compartmerit, means for supplying pressurized charging air to said engine including a casing, a compressor rotatably answer mounted within said casing, said compressor having an inlet connectable to the interior of said engine mounting compartment and a discharge connectable to said engine, silencer means associated with the inlet of said compressor and defining an intake duct connecting the inlet of said compressor means to the interior of said compartment, a first fan means associated with said intake duct and operable to impart limited pressure and swirl to the air flowing to the compressor inlet and to refiectively dampen substantially unidirectional high frequency sound waves emanating from the inlet of said compressor, an annular discharge manifold defined by said casing embracing the discharge of said compressor and being connected thereto by an annular diffuser, said annular discharge manifold having an arcuate outlet opening therein, a cylindrical heat exchange matrix embracing said annular manifold and supported by said casing for rotation past said manifold opening, seal means interposed between said matrix and said casing and cooperating therewith to define a matrix cooling chamber and a compressed air cooling chamber, passage means connecting said air cooling chamber to said engine, said silencer means and said casing defining a cooling air duct therebetween embracing said silencer and interconnecting said compartment with the atmosphere outside said compartment through said matrix cooling chamber, secondary fan means associated with said first fan means and onerable to induce cooling air flow through said cooling air duct and matrix, and means operable to drive said compressor, said matrix, and said fan means at different rotative speeds proportionate to and varying in accordance with the operation of the engine.

8. A power plant installation comprising, in combination, a housing member having an engine compartment therein, an internal combustion engine mounted in said engine compartment, filter means connecting the interior of said compartment to the atmosphere outside said housingmember, means for supplying pressurized charging air to said engine including a casing, a compressor rotatably mounted within said casing, said compressor having an inlet connected to the interior of said engine mounting compartment and a discharge connectable to said engine, silencer means associated with the inlet of said compressor and including a first fan means operable to dampingly reflect substantially unidirectional high frequency sound waves emanating from the inlet of said compressor, a discharge manifold connected to the discharge of said compressor and having an opening therein, a cylindrical heat exchange matrix supported by said casing for rotation past said manifold opening, seal means interposed between said matrix and said casing and cooperating therewith to define a matrix cooling chamber and a compressed air cooling chamber, said air cooling chamber being connected to said engine and said matrix cooling chamber interconnecting said compartment to the atmosphere outside said housing member, second fan means operable to induce cooling air flow through said matrix and cooling chamber from said compartment to the atmosphere, and means operable to drive said compressor, said matrix and said fan means at predetermined proportionate rotative speeds varying in accordance with engine operation.

9. A power plant comprising, in combination, a housing member having an engine compartment therein, an internal combustion engine mounted in said engine compartment, filter means connecting the interior of said compartment to the atmosphere outside, compressor means operable to supply pressurized charging air to said engine, said compressor means having an inlet connected to the interior of said engine mounting chamber and a discharge connected to said engine, a relatively low pressure induction fan means associated with the inlet of said compressor and operable to dampingly reflect high frequency sound waves emanating from the inlet of said compressor, and means operable to drive said compressor means and said fan means at predetermined proportionate rotative speeds varying in accordance with engine operation, said drive means being operable to drive said fan means at a substantially lower rotative speed than its driving speed of said compressor means.

10. In a power plant, the combination comprising, an internal combustion engine, a high speed rotary compressor having an inlet connectable to atmosphere and a discharge connectable to supply pressurized charging air to the engine, turbine means operable to drive said compressor in accordance with engine exhaust gases supplied thereto, manifold means for supplying engine exhaust gases through said turbine means, mechanical drive means intermediate the engine and the compressor and including overrunning means operable to drivingly connect said compressor to said engine when said mechanical drive means is being driven faster than said turbine means and operable to disconnect said compressor from said engine whenever said turbine means is being rotatably driven faster than said mechanical drive means whereby said compressor is partially engine driven when said mechanical drive means is being driven faster than said turbine means and said turbine drive means is permitted to overrun said mechanical drive means whenever said turbine drive means is being driven faster than said mechanical drive means, silencer means associated with the inlet of said compressor and defining an annular intake 'duct converging toward the inlet of said compressor, a first fan means intersecting said annular duct intermediate its ends and operable to impart limited pressure and swirl to the air flowing to the compressor inlet and to reflect the substantially unidirectional high frequency sound waves emanating from the inlet of said compressor thereby dampening such sound waves, an annular discharge manifold embracing the discharge of said compressor and being connected thereto through an annular diffuser, said discharge manifold having an outlet opening therein, passage means connecting said outlet opening to said engine,

a cylindrical heat exchange matrix embracing said annular manifold and supported by said casing for rotation between said manifold opening and said passage means, cooling air duct means for directing cooling air through said matrix outside said manifold opening, seal means interposed between said matrix, said manifold and passage means and said cooling air duct means and cooperating therewith to define a matrix cooling chamber, a second fan means drivingly connected to said first fan means and operable to induce cooling air flow through said matrix from the interior of said compartment to the atmosphere, and means for drivingly connecting said matrix and said fan means to said engine and operable to drive said matrix and said fan means at different speeds proportionate to and varying in accordance with the engine operating speed.

11. in combination, a high speed rotary compressor capable of generating high frequency sound waves and having an air inlet and a pressurized air discharge connectable to a sound attenuating system, silencer means including an intake duct connected to the inlet of said compressor and lined with sound absorbing material, and fan means intersecting said intake duct and operable to impart limited pressure and swirl to the air flowing through said intake duct to the compressor inlet to increase the pumping efficiency and air flow characteristic of the compressor, said fan means being further capable of deflecting and reflecting the substantially unidirectional high frequency sound waves generated by and emanating from the inlet of said compressor against the lined sound absorbing side walls of said intake duct and toward the compressor inlet thereby damping such high frequency sound waves.

12. The combination set forth in claim 11 and including means for rotatively driving said compressor and fan means at proportionate speeds, the driven speed of said 1? fan means being substantially slower than the'driven speed of said compressor.

13. The combination set forth in claim 11 and including means for rotatively driving said fan means at a speed proportionate to the primary frequency generated by said compressor.

14. In combination, a high speed rotary compressor capable of generating substantially unidirectional high frequency sound waves and having a fluid inlet opening and a pressurized fluid discharge opening connectable to a sound attenuating pressure receiving system, silencer means including an intake duct connected to the inlet opening of said compressor, fan means intersecting said intake duct and operable to impart limited swirl to the air flowing through said intake duct to the compressor inlet thereby increasing the pumping efficiency and air flow characteristic of the compressor, said fan means being further capable of deflecting and reflecting at least a portion of the substantially unidirectional high frequency sound waves emanating from the inlet of said compressor back toward the compressor inlet in out-of-phase relation thereby damping the generated high frequency sound "ayes, and means for rotatively driving said compressor and fan means at substantially proportionate speeds, the driven speed of said fan means being substantially slower than the driven speed of said compressor.

15. A silencer for a high frequency sound generator such as a high speed rotary compressor and having a sound emitting opening therein, said silencer comprising a duct member connectable at one end to the sound generator opening and lined with a sound absorbing material, rotary baflle means intersecting said duct and operable to deflect at least a portion of the substantially uudirectional high frequency sound waves against the line sound absorbing side walls of the duct and back toward said one end of the duct in out-of-phase relation thereto thereby damping the sound waves entering said one end, and means for rotatively driving said bafiie means at a relatively low speed proportional to the primary frequency being generated by said generator.

16. A silencer for a sound generator capable of gen erating substantially unidirectional high frequency sound waves such as a high speed rotary compressor and having a sound emitting opening therein, said silencer including a duct connectable at one end to the opening in the sound generator, rotary bafile means intersecting said duct and operable to deflect the generated high frequency sound waves entering said one end against the side walls of said duct and back toward said one end in out-ofphase relation to the generated high frequency sound waves thereby damping such sound waves, and means for rotatively driving said bafifle means at a relatively low speed proportional to the primary frequency being generated by said generator.

17. A silencer for a wide spectrum of substantially unidirectional high frequency sound including a duct of annular cross-section connectable to and converging toward an opening of a high frequency sound emitting source, rotary baflie means intersecting said duct intermediate its ends, said bafiie means being operable to refleet at lea-st a portion of the high frequency sound waves toward the side walls of said duct and back toward the sound emitting source in out-of-phase, damping relation to the waves emanating therefrom, and means for rotatively driving said baffle means at a speed proportional to the primary frequency of the sound emanating from the source.

18. In a silencer as set forth in claim 17, said duct being lined with sound absorbing material of tapered radial dimension.

19. A silencer for substantially unidirectional high frequency sound including a duct lined with sound absorbing material and connectable at one end to a source of such high frequency sound, a first portion of said duct adjacent to said source connectable end being defined by two radially spaced frusto-conical cylindrical wall members converging toward said source connectable end, a second portion of said duct distal from said source connectable end being defined by two radially spaced cylindrical members of constant radial dimension and axially aligned with said first duct portion, rotary baffie means intersecting said duct intermediate its ends and operable to deflect the unidirectional hgh frequency sound waves emanating from the source connectable end against the lined sound absorbing side walls of said duct and back toward the source connectable end in out-of-phase, wavedamping relation to the high frequency sound emanating therefrom, means for rotatively driving said bafile means at a relatively low speed proportional to the primary frequency of the sound emanating from said source connectabie end, a first stationary bafiie means mounted in spaced relation adjacent to the other end of said duct comprising a circular plate mounted normal to and in axial alignment with the common axis of said duct portions, a plurality of plates mounted in parallel spaced relation on said circular plate and tapered to form a plurality of acoustical wedges normal to and extending toward the adjacent end of said duct, said parallel plates being lined with a sound absorbing material and providing a tapered sound absorbing thickness to said material longitudinally of said parallel plates thereby varying the optimum sound wave absorbing characteristic of said material presented to the adjacent end of said duct to broaden the frequency absorption spectrum of said first stationary baffle means, and a cylindrical member embracing said circular plate and extending longitudinally therefrom to define a side wall of a length embracing said parallel plates and plate lining material, and a second stationary bai'file means including an annular casing member of angled cross-section having a radially extending flange closely embracing said other end of said duct and a longitudinally extending flange spacedly embracing the cylindrical wall member of said first stationary bafiie means, said annular casing member being lined with sound absorbing material, said first and second stationary bafile means being dimensioned and mounted in such spaced relation to each other and to the adjacent end of said duct that a cone generated by a line extending between the adjacent end of the duct and the distal end of said casing member intersects the duct adjacent end of said cylindrical wall member.

20. A silencer for unidirectional high frequency sound waves including a duct connectable at one end to a source of such hi h frequency sound, as least a portion of said duct being defined by two radially spaced frusto-conical cylindrical wall members converging toward said one end and lined with a sound absorbing material, a target baffie means mounted in spaced relation adjacent to the other end of said duct and comprising a circular plate mounted normal to and in axial alignment to the axis of said duct, a plurality of plates mounted in parallel spaced relation on said circular plate and being tapered to form a plurality of acoustical wedges normal to and extending toward the adjacent end of said duct, said parallel plates each being lined with a sound absorbing material to provide a tapered sound absorbing thickness to said material longitudinally of said parallel plates toward the adjacent end of said duet thereby varying the optimum sound wave absorbing characteristic of said material, and a cylindrical member embracing said circular plate and extending longitudinally therefrom to define a side wall of a length embracing said parallel plates and lining material, and a directionalizing bafide means including an annular casing member of angled cross-section having a first longitudinally extending flange spacedly embracing the cylindrical wall member of said target baffle means and a second flange extending radially inwardly therefrom and closely embracing said adjacent end of said duct, the inner surfaces of said first and second flanges of said casing member being lined with sound absorbing sprtgr'sl material, and said first and second bafiie means being dimensioned and mounted in such spaced relation to each other and to the adjacent end of said duct that a cone generated by a line extending between the inner surface of the opening defined by the adjacent end of the duct and the distal end of said casing member intersects said cylindrical wall member.

21. A silencer for substantially unidirectional high frequency sound waves comprising a member connectable to and defining a duct divergent from a source of such high frequency sound, a target bafile means mounted in spaced relation adjacent to the divergent end of said duct and comprising a first plate mounted normal to the adjacent divergent end of said duct, a plurality of plates mounted in parallel spaced relation to each other on said first plate and tapered to form a plurality of acoustical wedges normal to and extending toward the adjacent end of said duct, said parallel plates being lined with a sound absorbing material to present a tapered sound absorbing thickness of said material longitudinally of said parallel plates toward the adjacent end of said duct, thereby varying the optimum sound wave absorbing characteristic of said material, said first plate having a side wall extending longitudinally therefrom and embracing said parallel plates and lining material, a directionalizing baflle means including a casing member lined with sound absorbing material and closely embracing the divergent adjacent end of said duct and spacedly embracing the wall extending from said first plate, and said baffle means being dimensioned and mounted in such spaced relation to each other and to the adjacent divergent end of said duct that any line extending between the inner surface of the adjacent end of the duct and the distal end of said casing member intersects said wall.

22. A silencer for a device generating substantially unidirectional high frequency sound waves and having a sound emitting opening therein, said silencer including a target bafile mounted in spaced relation to said opening and comprising a recessed plate exceeding the size of said opening and having a bottom Wall in spaced parallel relation to said opening and a peripheral wall extending longitudinally toward said opening, a plurality of plates mounted in parallel spaced relation to each other on said plate within the recess defined by said peripheral wall and being tapered to form a plurality of acoustical wedges normal to and extending toward said opening, said wedge plates being lined with sound absorbing material of tapered sound absorbing thickness longitudinally of said opening to provide a variation in the optimum sound wave frequency absorption characteristic of the material, and a directionalizing bafiie including a casing member internally lined with sound absorbing material, said casing member extending from said opening and embracing said target battle in limited spaced relation thereto preventing any straight-line emission of high frequency sound therebetween from said opening.

23. A silencer for a device generating substantially unidirectional high frequency sound waves and having a sound emitting opening therein, said silencer comprising a target plate exceeding the size of said opening, a plurality of relatively thin acoustical wedges carried by said plate and tapered toward said opening, said wedges defining a plurality of recesses therebetween, sound absorbing material covering said wedges and substantially filling the recesses therebetween, and said silencer being mounted in limited parallel spaced relation to said opening thereby tending to prevent straight-line emission of high frequency sound therebetween, said silencer wedges deflecting a portion of the generated high frequency sound waves for dissipation by said sound absorbing material and said target plate reflecting a portion of the generated high frequency waves back toward said opening in out-of-phas'e relation tending to dampen the sound waves emitting from the opening.

24. A high speed rotary compressor mechanism capable of generating a wide spectrum of substantially unidirectional high frequency sound waves and comprising a casing defining a compressor chamber and having inlet and outlet openings therein, said outlet opening being connectable to a pressure receiving system, a compressor impeller rotatably mounted in said compressor chamber and operable to deliver pressurized air to said outlet opening, a cylindrical heat exchange matrix supported by said casing for rotation past said outlet opening, said casingdefining a compressed air cooling chamber adjacent saidoutlet opening and a matrix cooling chamber, said compressed air cooling chamber being connected to said pressure receiving system, a first fan means operable to induce cooling air flow through said matrix within said matrix cooling chamber, a first silencer means including an intake duct connected at one end thereof to the inlet opening and lined with sound absorbing material, a second fan means operable to impart limited swirl to the air flowing through the intake duct to the compressor inlet and impeller, said second fan means including a plurality of fan blades capable of deflecting and reflecting a portion of the substantially unidirectional high frequency sound Waves emanating from the inlet against the lined sound absorbing side Walls of said intake duct and back toward the compressor inlet thereby damping such high frequency sound waves, secondary silencer means associated with the end of said intake duct distal from said compressor inlet and comprising a target plate parallel to and exceeding the size of said adjacent duct end, a plurality of relatively thin acoustical wedges carried by said plate and tapered toward said intake duct, said wedges defining a plurality of recesses therebetween, sound absorbing material covering said wedges and substantially filling the recesses therebetween, and said secondary silencer means being mounted in limited parallel spaced relation to said adjacent duct end thereby tending to prevent any straight-line emission of high frequency sound waves therebetween from said duct, said silencer wedges deflecting a portion of such high frequency sound waves for dissipation by said Wedge covering material and said target plate reflecting a portion of such high frequency waves back into said duct in out-of-phase relation tend= ing to dampen such waves passing said second fan means, and means operable to drive said compressor impeller at a relatively high speed and including means for driving said matrix and said fan means at relatively slow speeds proportional to the impeller driven speed.

25. A high speed rotary compressor mechanism capable of generating a wide spectrum of substantially unidiree tional high frequency sound waves comprising a casing defining a compressor chamber and having inlet and outlet openings therein,'said outlet opening being connectable to a pressure receiving system, a compressor impeller rotatably mounted in said compressor chamber and 0perable to deliver pressurized air to said outlet opening, said casing defining a compressed air cooling chamber adjacent said outlet opening, said compressed air cooling chamber being connected to said pressure receiving system, said casing further defining a matrix cooling chamber, a cylindrical heat exchange matrix supported by said casing for rotation through said cooling chambers, a first fan means including a first plurality of fan blades operable to induce cooling air flow through said matrix within said matrix cooling chamber, silencing means including an intake duct connected at one end thereof to the inlet opening and lined with sound absorbing material, a second fan means including a second plurality of fan blades operable to impart limited swirl to the air flowing through the intake duct to the compressor inlet and impeller, said second fan blades being capable of deflecting and reflecting a portionof the substantially unidirectional high frequency sound Waves generated by and emanating from the inlet of the compressor against the lined sound absorbing side walls of said'intake duct and back towardthe compressor inlet thereby damping such high frequency sound waves,

means operable to drive said compressor impeller at a relatively high speed, and means for driving said matrix and said fan means at speeds proportional to the impeller driven speed.

26. A high speed rotary compressor mechanism capable of generating a wide spectrum of substantially unidirectional high frequency sound waves comprising a casing defining a compressor chamber having inlet and outlet openings leading thereto, an impeller rotatably mounted in said compressor chamber and operable to deliver pressurized air to said outlet opening, said casing defining a compressed air cooling chamber adjacent said outlet opening, said compressed air cooling chamber being connectable to a pressure receiving system, said casing further defining a matrix cooling chamber, a cylindrical heat exchange matrix supported by said casing for rotation through said cooling chambers, silencer means associated with the inlet of said compressor and including an intake duct connected at one end thereof to the inlet of said compressor chamber, a first fan means including a first plurality of fan blades intersecting said intake duct and operable to impart limited swirl to the air flowing through the intake duct to the compressor inlet and impeller, said first fan blades being capable of deflecting and reflecting a portion of the substantially unidirectional high frequency sound waves generated by and emanating from the inlet of the compressor against the side walls of said intake duct and back toward the compressor inlet thereby damping such high frequency sound waves, said intake duct and said casing defining a cooling air duct therebetween concentrically embracing said intake duct and connected to said matrix cooling chamber, a second fan means associated with said first fan means and including a second plurality of fan blades intersecting said cooling air duct and operable to induce cooling air flow through said cooling air duct and matrix, and driving means including means operable to drive said compressor impeller at a relatively high speed and including means for driving said matrix and said fan means at relatively slower speeds proportional to the impeller driven speed.

27. A compressor mechanism as set forth in claim 26 and including a second silencer means associated with the end of said intake duct distal from said compressor inlet and comprising a target plate parallel to and exceeding the size of said adjacent duct end, a plurality of relatively thin acoustical wedges carried by said plate and tapered toward said intake duct, said wedges defining a plurality of recesses therebetween, sound absorbing mate rial covering said wedges and substantially filling the recesses therebetween, and said secondary silencer means being mounted in limited parallel spaced relation to said adjacent duct end thereby tending to prevent straightline emission of high frequency sound waves therebetween from said duct, said silencer wedges deflecting a portion of such high frequency sound Waves for dissipation by said wedge covering material and said target plate reflecting a portion of such high frequency Waves back into said duct in out-of-phase relation tending to dampen such waves passing said first fan means.

28. In a compressor mechanism as set forth in claim 26, a second silencer means including a target baflie mounted in spaced relation to the other end of said intake duct and comprising a circular plate mounted normal to the axis of said duct, said circular plate being diametrically larger than the adjacent end of said intake duct, a plurality of relatively thin acoustical wedges carried by said circular plate and tapered toward the adjacent end of said duct, said wedges defining a plurality of recesses therebetween, sound absorbing material covering said wedges and substantially filling said recesses, a cylindrical peripheral wall carried by said circular plate and extending longitudinally therefrom to define a side wall of a length embracing said parallel plates and lining material, said silencer wedges deflecting a portion of any high frequency sound waves emanating from said intake duct for dissipation by said wedge covering material and said target plate reflecting a portion of such high frequency waves back into said duct in out-of-phase relation tending to dampen such waves passing said first fan means, and a directionalizing baflle including an annular casing member of angled cross-section closely embracing said other end of said duct and spacedly embracing the cylindrical wall member of said first stationary baffle means, said annular casing member being lined with sound absorbing material, said target and directionalizing baflle means being dimensioned and mounted in such spaced relation to each other and to the adjacent end of said duct that a cone generated by a line extended between the adjacent end of the duct and the distal end of said casing member intersects said cylindrical Wall member.

29. A high speed rotary compressor mechanism comprising a casing defining a compressor chamber having inlet and outlet openings leading thereto, animpeller rotatably mounted in said compressor chamber and operable to deliver pressurized air to said outlet opening, said casing defining a compressed air cooling chamber adjacent said outlet opening, said compressed air cooling chamber being connectable to a pressure receiving system, said casing further defining a matrix cooling chamber, a cylindrical heat exchange matrix supported by said casing for rotation through said cooling chambers, an intake duct connected at one end thereof to the inlet, said intake duct and said casing defining a cooling air duct therebetween concentrically embracing said intake duct and connected to said matrix cooling chamber, a fan member having a first plurality of fan blades intersecting said intake duct and operable to impart limited swirl to the air flowing through the intake duct to the compressor inlet and impeller and having a second plurality of fan blades intersecting said cooling air duct and operable to induce cooling air flow through said cooling air duct and matrix, and means for driving said compressor impeller at a relatively high speed and including means for driving said matrix and said fan means at relatively slower speeds proportional to the impeller driven speed.

30. A silencer for a high speed rotary compressor mechanism having an impeller rotatably driven at a relatively high speed and operable to deliver pressurized air to an outlet opening and generating substantially unidirec tional high frequency sound waves capable of echoic transmission from an inlet opening, said silencer comprising an intake duct connectable at one end thereof to the sound transmitting inlet of the compressor and terminating at its opposite end in an annular bell generated by an arc diverging radially and longitudinally outwardly from said one end, and silencer means associated with said opposite end of the intake duct and comprising a circular target plate of a diameter exceeding that of said intake duct bell, a plurality of relatively thin acoustical wedges carried by said plate and tapered toward said intake duct, said wedges defining a plurality of recesses therebetween, and sound absorbing material covering said wedges and substantially filling the recesses therebetween, said silencer means being mounted in limited parallel spaced relation to and coaxially of said duct bell end thereby preventing straight-line transmission of high frequency sound waves therebetween from said intake duct, said silencer wedges deflecting a portion of such high frequency sound waves for dissipation by said wedge covering material and said target plate reflecting a portion of such high frequency waves back into said duct in out-of-phase relation tending to dampen such waves.

31. A silencer for a high speed rotary compressor mechanism having inlet and outlet openings and an impeller rotatably driven at a relatively high speed and operable to deliver pressurized air to said outlet opening and generating substantially unidirectional high frequency sound Waves capable of echoic transmission from the inlet opening, said silencer comprising an intake duct connectable at one end thereof to the sound transmitting inlet of the. compressor and terminating at its opposite end in an annular bell generated by an arc diverging radialiy and longitudinally outwardly from said one end, a target baiiie mounted in spaced relation to said intake bell and comprising a circular plate mounted normal to the axis of said duct, said circular plate being diametrically larger than the periphery of said intake bell, a plurality of relatively thin acoustical wedges carried by said circular plate and tapered toward the adjacent end of said duct, said Wedges defining a plurality of recesses therebetween, sound absorbing material covering said wedges and substantially filling said recesses, a cylindrical peripheral wall carried by said circular plate and extending longitudinally therefrom to define a side wall of a length embracing said parallel plates and lining material, said silencer wedges deflecting a portion of the high frequency sound waves emanating from said intake duct for dissipation by said wedge covering material and said target plate reflecting a portion of such hi h frequency sound waves back into said intake bell and duct in outof-phase relation thereby tending to dampen the high frequency sound waves passing outwardly of said duct, and a directionalizing bafile including an annular casing member of angled cross-section closely embracing the outer periphery of said intake bell and spacedly embracing the cylindrical Wall member of said first stationary baffle means, said annular casing member being lined With sound absorbing material, and said target and -directionalizing bafi'les being dimensioned and mounted in such spaced relation to each other and to the adjacent end of said bell that said cylindrical wall intersects any line tangent to the inner surface of said bell passing through the distal end of said casing member thereby preventing such high frequency sound Waves from passing between said baffles in a straight line.

32. In combination, a housing member having an engine compartment therein, an internal combustion engine mounted in said compartment, a high speed rotary compressor operable to supply pressurized charging air to the engine, said compressor having an inlet connectable through said compartment to the atmosphere outside the 24 housing member and a discharge connected to the engine, silencer means associated with the inlet of the compressor and including an intake duct connecting the compressor inlet to the interior of the compartment, said housing compartment and intake duct defining an acoustical impedance means operable to damp the primarily unidirectional high frequency sound Waves generated by and emanating from the inlet of the compressor, said engine constituting a high frequency sound attenuating mean connected to the compressor discharge, fan means operable to impart limited pressure and swirl to the air flow induced through said intake duct to the compressor inlet thereby increasing the efficiency and airflow pumping characteristics of the compressor, said fan means being further capable of reflective damping of the substantially unidirectional high frequency sound wave emanating from the inlet of the compressor, and drive means intermediate the engine and compressor and the fan means and operable to drive both said compressor and fan means at rotative speeds proportional to the speed of the engine with the driven speed of said fan means being substantially lower than the sound-generating and air-iiow-inducing driven speed of the compressor.

References ited in the file of this patent UNITED STATES PATENTS 2,160,666 McMahan May 30, 1939 2,267,275 Gevrenz Dec. 23, 1941 2,313,244 Jones Mar. 9, 1943 2,353,998 Cortez July 18, 1944 2,397,941 Birkigt Apr. 9, 1946 2,402,725 Birkigt June 25, 1946 2,434,726 Udale Jan. 20, 1948 2,585,968 Schneider Feb. 19, 1952 2,646,027 Ackerman et al July 21, 1953 2,647,372 Fell Aug. 4, 1953 2,714,881 Bancel Aug. 9, 1955 2,749,998 Walton et a1 June 12, 1956 2,801,518 Wosika et al. Aug. 6, 1957 2,869,670 Hoffman Ian. 20, 1959 2,916,026 Eoit et al Dec. 8, 1959 2,929,198 Crocchi Mar. 22, 1960 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,077,731 February 19, 1963 Albert N, Addie et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 32, strike out "in"; column 3, line 73,

for "accesory" read accessory column 6, linell, for "for" read are column 14, line 3, for "wtih" Iad+. with line 70, for "combinaation" read combination column 18, line 8, for "hgh" read high Signed and sealed this 14th day of April 1964.

(SEAL) Au t: ERNZI ST w. SWIDER EDWARD BRENNER Attesting Officer v Commissioner of Patents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No 3,077,731 February 19, 1963 Albert N. Addie et al.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 1, line 32, strike out "in"; column 3, lines 73,

for "accesory" read accessory column 6, line...l 1 "for" read are column 14, line 3, for "wtih" reads..n,v with line 70, for "combinaation" readcombination column 18, line 8, for "hgh" read high Signed and sealed this 14th day of April 1964 (SEAL) An; st: ERN EST w. SWIDER EDWARD BRENNER Attesting Officer Commissioner of Patents 

1. IN COMBINATION, A HOUSING MEMBER HAVING AN ENGINE COMPARTMENT THEREIN, AN INTERNAL COMBUSTION ENGINE MOUNTED IN SAID COMPARTMENT, FILTER MEANS CONNECTING THE INTERIOR OF SAID COMPARTMENT TO THE ATMOSPHERE OUTSIDE THE COMPARTMENT, MEANS FOR SUPPLYING PRESSURIZED CHARGING AIR TO SAID ENGINE INCLUDING A CASING, A COMPRESSOR ROTATABLY MOUNTED WITHIN SAID CASING, SAID COMPRESSOR HAVING AN INLET CONNECTABLE TO THE INTERIOR OF SAID ENGINE MOUNTING COMPARTMENT AND A DISCHARGE CONNECTABLE TO SAID ENGINE, SAID COMPARTMENT AND FILTER MEANS DEFINING ACOUSTICAL IMPEDANCE MEANS OPERABLE TO DAMP THE SOUND WAVES GENERATED BY AND EMANATING FROM SAID COMPRESSOR AND SAID ENGINE CONSTITUTING A HIGH FREQUENCY SOUND ATTENUATING MEANS CONNECTED TO SAID COMPRESSOR DISCHARGE, TURBINE MEANS OPERABLE TO ROTATIVELY DRIVE SAID COMPRESSOR AT A RELATIVELY HIGH SPEED IN ACCORDANCE WITH ENGINE EXHAUST GASES SUPPLIED THERETO, MANIFOLD MEANS FOR SUPPLYING ENGINE EXHAUST GASES TO SAID TURBINE MEANS AND THEREFROM TO THE ATMOSPHERE OUTSIDE THE COMPARTMENT, MECHANICAL DRIVE MEANS INTERMEDIATE THE ENGINE AND THE COMPRESSOR AND INCLUDING OVERRUNNING MEANS OPERABLE TO DRIVINGLY CONNECT SAID COMPRESSOR TO SAID ENGINE UNDER LOW EXHAUST GAS SUPPLY CONDITIONS TO SAID TURBINE, SAID DRIVE MEANS BEING OPERABLE TO DISCONNECT SAID COMPRESSOR FROM SAID ENGINE WHENEVER SAID TURBINE MEANS IS ROTATABLY DRIVEN FASTER THAN SAID MECHANICAL DRIVE MEANS, WHEREBY SAID COMPRESSOR IS PARTIALLY ENGINE DRIVEN WHEN SAID MECHANICAL DRIVE MEANS IS BEING DRIVEN FASTER THAN SAID TURBINE MEANS AND SAID TURBINE DRIVE MEANS IS PERMITTED TO OVERRUN SAID MECHANICAL DRIVE MEANS WHENEVER SAID TURBINE DRIVE MEANS IS BEING DRIVEN FASTER THAN SAID MECHANICAL DRIVE MEANS, HIGH FREQUENCY SILENCER MEANS ASSOCIATED WITH THE INLET OF SAID COMPRESSOR AND DEFINING AN ANNULAR INTAKE DUCT CONVERGING TOWARD AND CONNECTING THE INLET OF SAID COMPRESSOR TO THE INTERIOR OF SAID COMPARTMENT, A FIRST FAN MEANS INTERSECTING SAID SILENCER DUCT AND OPERABLE TO IMPART LIMITED PRESSURE AND SWIRL TO THE AIR FLOWING TO THE COMPRESSOR INLET THEREBY INCREASING THE EFFICIENCY AND AIR FLOW CHARACTERISTICS OF THE COMPRESSOR AND TO REFLECTIVELY DAMPEN SUBSTANTIALLY UNIDIRECTIONAL HIGH FREQUENCY SOUND WAVES EMANATING FROM THE INLET OF SAID COMPRESSOR, DRIVE MEANS INTERMEDIATE SAID ENGINE AND SAID FIRST FAN MEANS, AN ANNULAR DISCHARGE MANIFOLD DEFINED BY SAID CASING AND EMBRACING THE DISCHARGE OF SAID COMPRESSOR AND CONNECTED THERETO BY AN ANNULAR DIFFUSER, SAID ANNULAR DISCHARGE MANIFOLD HAVING AN ARCUATE OUTLET OPENING THEREIN, A CYLINDRICAL HEAT EXCHANGE MATRIX EMBRACING SAID ANNULAR MANIFOLD AND SUPPORTED BY SAID CASING FOR ROTATION PAST SAID MANIFOLD OPENING, SEAL MEANS INTERPOSED BETWEEN SAID MATRIX AND SAID CASING AND COOPERATING THEREWITH TO DEFINE A MATRIX COOLING CHAMBER AND A COMPRESSED AIR COOLING CHAMBER, PASSAGE MEANS INCLUDING SOUND ATTENUATING IMPINGEMENT FILTER MEANS CONNECTING SAID AIR COOLING CHAMBER TO SAID ENGINE, MEANS FOR DRIVINGLY CONNECTING SAID MATRIX TO SAID ENGINE, SAID SILENCER MEANS AND SAID CASING DEFINING A COOLING AIR DUCT THEREBETWEEN EMBRACING SAID INTAKE DUCT, SAID COOLING AIR DUCT CONNECTING SAID MATRIX COOLING CHAMBER TO THE INTERIOR OF SAID COMPARTMENT AND TO THE ATMOSPHERE OUTSIDE SAID COMPARTMENT, AND A SECOND FAN MEANS DRIVINGLY CONNECTED TO SAID FIRST FAN MEANS AND OPERABLE TO INDUCE COOLING AIR FLOW THROUGH SAID MATRIX FROM THE INTERIOR OF SAID COMPARTMENT TO THE ATMOSPHERE, SAID COOLING AIR DUCT AND THE RELATIVELY LOW VELOCITY COOLING AIR FLOW INDUCED THERETHROUGH COOPERATING TO INSULATE AND ATTENUATE SOUNDS TRANSMITTED RADIALLY OUTWARDLY OF SAID INTAKE DUCT. 